28
7 VG9H 70 en
Once you have the potentiometer inner section
aligned to correct resistance value, tighten the
potentiometer set screw to connect the potentiome-
ter firmly to the valve controller axis. Verify that the
resistance values stays between 400-600 ohms after
the tightening.
The potentiometer cable can now be connected
back to the transmitter board terminal pins. The
positioning of the terminal plug is done according to
valve operation orientation (see Fig. 39). The plug
must always be aligned to one end or the other of
the five pin terminal on the transmitter board.
Connect DC power to the correct positive and nega-
tive terminals in the terminal strip (see chapter 11.6
for wiring details).
Make sure the valve is stationary in closed position
and adjust the zero trimpot to give 4 mA output.
Operate the valve to desired open position.
Make sure the valve is stationery in open position
and adjust the span trimpot to give 20 mA output.
The zero and span adjustments are non-interactive.
8.6
Removal of the limit switches and position
transmitter for accessing the ValvGuard
Remove the cover (100) and the pointer (109).
Loosen the screws (314) in the cam disks (313) and
remove the cam disks and bushings (346) from the
shaft.
Remove the LUI cabling from the circuit board. Dis-
connect and remove all cabling which enters the
limit switch housing (300).
Remove screws (325), 3 pcs and lift out the limit
switch base plate (324) complete with switches, LUI
and connector block.
Open screw (326) and turn the limit switch housing
(300) from the positioner housing.
Remove the electronics cover (39).
Proceed with the ValvGuard as applicable.
Re-install the limit switch according to 8.2 andcheck
the adjustment according to 8.4.
8.7
Circuit diagrams
The internal circuitry of the limit switch is shown in the con-
nection diagrams in 11.6.
8.8
Maintenance
Regular maintenance of the limit switch is not necessary.
9
TOOLS
Following tools are needed for the product installation and
service:
Flat screwdriver
0.5 x 3.0 x 75 mm
Torx screwdriver
T10
T20
Hexagon screwdrivers
3 mm
6 mm
10
ORDERING SPARE PARTS
Spare parts are delivered as modules. The modules availa-
ble are indicated in 11.1.
When ordering spare parts, always include the following
information:
type code, sales order number, serial number
number of the parts list, part number, name of the
part and quantity required
This information can be found from the identification plate
or documents.
Fig. 38
Potentiometer operation.
Fig. 39
Plug setting for transmitter operation.
Ex WARNING:
The locking screw of the limit switch housing (Part
326) is essential to explosion protection.
The limit switch housing has to be locked in place for Ex d
protection. The screw grounds the limit switch housing to
the housing of the ValvGuard.
